Diphenylamine-metal polysulfide reaction products and method of preparing same



the oil.

.atoms, preferably 1 to carbon atoms. is carried out at an elevated temperature and for a 2,848,444 Patented Aug. 19, 1958 tun! DIPHENYLAMINE-Ml jl'.A-.L POLYSULFIDE REAC- TION PRODUCTS AND METHOD OF PREPAR- ING SAME No Drawing. Application May 25, 1955 Serial No. 511,104

10 Claims. or. 260133) This invention relates to lubricants and more particularly relates to improved lubricant compositions containing a new class of products as corrosion and oxidation inhibitors, to the novel products themselves and to the method of their preparation. The novel products i of this invention, which are oil soluble, are prepared by reacting a metal polysulfide with diphenylarnine or an alkyl derivative thereof.

The successful lubrication of internal combustion engines is complicated by the deterioration of the lubricating oil during use. Oxidation of the oil, for example, causes the formation of sludge and lacquers that deposit on parts of the engine and interfere with circulation of Also, certain deterioration products are acidic in nature and corrode bearing metals and other metal parts. The difiiculties encountered in regard to corrosion have become aggravated in recent yeears because of the increasing utilization of bearings made of alloys such as cadmium-nickel, copper-lead, cadmium-silver, etc., and also because of the increased severity of engine operation. Although the discovery of certain lubricant additives has alleviated this problem to a certain extent, there is a continuing need for still further improved lubricating compositions which are resistant to oxidation.

products of this invention are prepared by reacting a metal polysulfide, preferably a polysulfide of a metal selected from the group consisting of alkali metals and alkaline earth metals with a compound having the formula where R is selected from the group consisting of hydrogen atoms and alkyl radicals containing 1 to 16 carbon The reaction period of time sufiicient to produce an oil-soluble reaction product which contains a ratio of sulfur atoms to nitrogen atoms in the range of about 0.4 to 1.5, preferably about 0.5 to 1.0. The proportions of the reactants are selected so that the amountof the metal polysulfide I employedin the reaction is such as to provide sufiicient reactive sulfur atoms to produce an oil-soluble reaction product containing the aforementioned sulfur to nitrogen'ratio, The reaction mixture (resulting from -the reaction of the ;metal polysulfide and the diphenyl- :amine compound) will generally contain a small amount .of oil-insolublematerial and this is removed by filtration or decantation from oil solution (e. g. hexane) to yield the oil-soluble produce of this invention.

The metal polysulfides of this invention have the following general formula:

where M is preferably an alkali metal or an alkaline earth metal, a is an integer of 2 in the case of alkali metals and 1 in the case of alkaline earth metals and b is an integer of value 2 to 5. The preferred metals are calcium, barium, magnesium, lithium, sodium, and p0- tassium. The alkaline earth metals are particularly preferred. The preferred metal polysulfide is calcium polysulfide. it has been found that metal monosulfides alone are inoperative in the present invention. The metal polysulfides utilized in this invention may be prepared by any conventional methods such as by heating 1 mole of the metal monosulfide with about 1 to 4 moles, particularly about 3 moles, of elemental sulfur. Such reaction may be conveniently carried out at a temperature in the range of about 200 to 300 F. for a period of time of about 0.52 hours. In this type of preparation it is desirable to carry out the reaction in water which serves as a vehicle or carrier for the reactants. The products produced by reacting metal monosulfides with elemental sulfur are predominantly metal polysulfides, and the total product may be employed in this invention if desired. The reaction of the metal polysulfide and the phenylamine compound is carried out at an elevated temperature so that the reactants are maintained in a molten state. Temperatures in the range of about F. to 570 F. may be employed to carry out the reaction. At temperatures below about 175 F. the reactants will not readily react whereas at temperatures in excess of about 570 F. ditficulty is encountered due to the vaporization of the diphenylamine compound. Preferably the reaction temperature is maintained in the range of about 200 to 300 F.

The proportion of the metal polysulfide employed in the reaction is such as to provide sufiicient reactive sulfur atoms to produce an oil-soluble reaction product containing a ratio of sulfur atoms to nitrogen atoms in the range of about 0.4 to 1.5, preferably 0.5 to 1.0. Because the higher sulfur content polysulfides contain a greater number of reactive sulfur atoms per molecule, it is therefore possible to utilize a smaller proportion of them in the reaction than in the case of the lower sulfur content polysulfides such as the disulfides. The term reactive sulfur atoms refers to those atoms of sulfur which are combined with the metal in excess of one sulfur atom per molecule. Thus the metal polysulfides may be expressed as MSS where y is an integer of 1 to 4 and 5,, designates the reactive sulfur atoms."

The reaction is carried out for an extended period of time until an oil-soluble reaction product is obtained which contains the desired ratio of sulfur atoms to nitrogen atoms, which ratio, as previously stated, is in the range of about 0.4 to 1.5, preferably about 0.5 to 1.0. A reaction time in the range of about 0.5 to 4.0 hours is generally sufficient to produce an oil-soluble reaction product containing a ratio of sulfur atoms to nitrogen atoms in the range of 0.4 to 1.5, providing, of course, that a suflicient quantity of the metal polysulfide is employed. Preferred reaction times are in the range of about 1 to 2 hours. Upon completion of the reaction, the compounds of this invention may be dissolved in a suitable solvent such as hexane, heptane, petroleum ether, ligroin, etc., and then filtered to separate therefrom any insoluble inorganic material such as metal monosulfides, metal oxides and other unreactive products. Thereafter the compounds of this invention may be recrystallized from the solvent. The crystallized product contains no detectable amount of metal, which EXAMPLE 1 A calcium polysulfide product was prepared by placing 72 grams of calcium monosulfide, 96 grams of sulfur, and 400 grams of water in a one-liter glass flask which was equipped with a condenser, stirrer, and thermometer. The contents of the flask were heated for about one hour at about 215 F., with the water being refluxed during the reaction. The reaction produced a red colored upper liquid layer and a small lower layer of unreacted solid materials. The red colored liquid was separated and was then evaporated to dryness to recover a yellow powder which contained 22% calcium and 57.5% sulfur. Although the calcium polysulfide product in this example was prepared as described above in the laboratory, it will be understood that any polysulfide of alkali or alkaline earth metals may be used in the reaction described below.

34 grams of the powder prepared above were then blended with 84 grams of diphenylamine and the mixture was placed in a one-liter glass flask equipped with a condenser, stirrer, and thermometer. The contents of the flask were heated together for two hours at 120 C. After cooling, the contents of the flask were blended with about 250 cc. of hexane and the solution was filtered through a Buchner funnel. A small amount of insoluble material was collected on the filter. This insoluble material consisted primarily of calcium monosulfide and other unreactive calcium and sulfur containing products. Thereafter the oil-soluble product of this invention was recrystallized from the hexane and dried to produce a crystalline product which contained 12.32% sulfur, 6.47% nitrogen and no detectable amount of calcium. The product was readily soluble in mineral oil and will hereinafter be termed product A. The ratio of sulfur atoms to nitrogen atoms in product A was 0.84.

A similar reaction was carried out utilizing diphenylamine and calcium monosulfide but no reaction took place, thus indicating the necessity of utilizing a polysulfide in the reaction with diphenylamine.

EXAMPLE 2 About 34 grams of the dried powder prepared in Example 1 were blended with 98.2 grams of p,p dioctyl diphenylamine and the mixture was placed in a one-liter glass flask equipped with a condenser, stirrer, and thermometer. The contents of the fiask were heated for one hour at 140 C., after which the contents were cooled and then added to about 250 cc. of hexane. The resultant solution was filtered through a Buchner funnel and a small amount of oil-insoluble material was collected on the filter. The oil-soluble product of this invention was then recrystallized from the filtrate and dried. An oil-soluble crystalline product was obtained which contained 4.02% sulfur, 3.37% nitrogen and no detectable amount of calcium. This product will hereinafter be termed product B. The ratio of sulfur atoms to nitrogen atoms in product B was 0.53.

EXAMPLE 3 In order to determine the storage stability of the oilsoluble reaction products of this invention in mineral lubricating oils, various concentrations of product A and product B-were added to a mineral lubricating oil base stock (hereinafter termed base stock I) and were tested for stability under the following conditions: (I) in the sunlight at room temperature and (2) in a refrigerator at 35 F. The storage stability of the blends was de termined by noting the period of time that they remained clear without any evidence of turbidity, suspended sediment or solids precipitation. An anti-oxidant additive of the prior art, namely phenothiazine, was also subjected to these storage stability tests for comparison purposes.

Table I.Storage stability test Additive in Base Stock I 1 Storage Stability, 1 Days Cone, Sunlight Refriger- Type Wt. Per- Room ator, 35

cent Temp. F.

1 Base Stock I was a solvent refined Mid-Continent mineral oil base stock (SAE-20 grade) having the following inspections:

EXAMPLE 4 The effectiveness of product A as an oxidation inhibitor was then determined in a test which was carried out as follows: A 500 cc. sample of the test lubricant was charged to a Pyrex tube in a salt bath held at 325 F. A shaft holding two halves of a copper-lead hearing was rotated in the test lubricant at 400 to 650 R. P. M. while 2 cu. ft./hour of air was bubbled through the lubricant. The test was run for 4-hour periods, and at the end of each, the bearings were cleaned and weighed to measure weight loss. The test was continued in repeated 4-hour cycles until a cumulative bearing weight loss of mgms. was obtained.

For comparison purposes, phenothiaz-ine was similarly tested and the following results were determined:

Table II.0xidation-c0rr0si0n test The results of the tests shown in Examples 3 and 4 clearly indicate that products made in accordance with this invention are outstanding additives for lubricating oil compositions on account of (1) their excellent solubility in lubricating oil base stocks and (2) their effectiveness in reducing oxidation and corrosion.

EXAMPLE 5 The products of this invention are not a mere mixture of diphenylamine (or its alkyl derivatives) and phenothiazine (or its alkyl derivatives), which can be formed by reacting diphenylamine (or its alkyl derivatives) with elemental sulfur. tory treatment of the product of this invention. A benzene solution of product A was washed with a 10% solution of hydrochloric acid and the water phase separated. If free diphenylamine had been present, it would have formed the diphenylamine hydrochloride salt which is Water soluble. The water layer was neutralized with sodium hydroxide to liberate free diphenylamine, which being water insoluble would precipitate. Since no precipitate was formed, it can be concluded that the product of the invention contains no free diphenylamine.

This is shown by the following labora-.

. Product A of this invention as well as diphenylamine, ,phenothiazine and mixtures of diphenylamine and phenotbiazine were evaluated as additives in a mineral lubricating oil in the oxidation-corrosion test described in Example 4. The mineral lubricating oil (hereinafter termed base stock H) was a solvent refined Mid-Continent mineral oil base stock of SAE-30 grade. The results of these tests are shown below:

Table III.Oxidation-crrosion test Diphenylamine When additives of this invention are employed in lubricating oils, they are usually added in proportions in the range of about 0.01 to 10.0% by weight and preferably in the range of about 0.1 to 5.0% by weight, particularly about 0.2 to 1.0% by weight. If the additives are utilized at high concentrations, conventional solubilizers may be employed to increase the solubility of these additives. The proportions giving the best results will vary somewhat according to the nature of the additive.

' The products of the present invention may be employed not only in ordinary hydrocarbon lubricating oils but also in the heavy duty type of lubricating oils which i have been compounded with such detergent type additives as phosphosulfurized hydrocarbons, metal soaps, metal petroleum sulfonates, metal phenates, metal alcoholates,

metal alkyl phenol sulfides, metal organo phosphates,

. thiophosphates, phosphites and thiophosphites, metal salicylates, metal xanthates and thioxanthates, metal thiocarbamates, amines and amine derivates, reaction products of metal phenates and sulfur, reaction products of metal phenates and phosphorus sulfides, metal phenol sulfonates and the like. Thus the additives of the present invention may be used in lubricating oils containing such other addition agents as barium tert.-octylphenol sulfide, calcium tert.-amylphenol sulfide, nickel oleate, barium octadecylate, calcium phenyl stearate, zinc diisopropyl salicylate, aluminum naphthenate, calcium cetyl phosphate, barium di-tert.-amylphenol sulfide, calcium petroleum sulfonate, zinc methylcyclohexyl thiophosphate, calcium dichlorostearate, etc.

The lubricating oil base stocks used in the compositions of this invention may be straight mineral lubricating oils or distillates derived from paraffinic, naphthenic, asphaltic, or mixed base crudes, or, if desired, various blended oils may be employed as well as residuals, particularly those from which asphaltic constituents have been carefully removed. The oils may be refined by conventional methods using acid, alkali and/or clay or other agents such as aluminum chloride, or they may be extracted oils produced, for example, by solvent extraction with solvents of the type of phenol, sulfur dioxide, furfural, dichlorodiethyl ether, nitrobenzene, crotonaldehyde, etc. Hydrogenated oils, white oils, or shale oil may be employed as well as synthetic oils, such as lubricating grade simple and complex esters of dibasic acids (e. g. di-Z-ethyl hexyl sebacate) carbonates and organic phenylates, polyethers, simple and complex formals, polyethyleneglycols, etc., as well as those prepared, for example, by the polymerization of olefins or by the reaction of oxides of carbon with hydrogen or by the hydrogenation of coal or its products. Also, for special applications, animal, vegetable or fish oils or their hydrogenated or voltolized products may be employed in admixture with mineral oils.

For the best results the'base stock chosen should normally be that oil which without the new additive present gives the optimum performance in the service contemplated. However, since one advantage of the additives ,is that their use also makes feasible the employment of less satisfactory mineral oils or other oils, no strict rule can be laid down for the choice of the base stock. Certain essentials must of course be observed. The oil must possess the viscosity and volatility characteristics known to be required for the service contemplated. The oil must be a satisfactory solvent for the additive, although in some cases auxiliary solvent agents may be used. The lubricating oils, however they may have been produced, may vary considerably in viscosity and other properties depending upon the particular use for which they are desired, but they usually range from about 40 to seconds Saybolt viscosity at 210 F. For the lubricating of certain low and medium speed Diesel engines the general practice has often been to use a lubricating oil base stock prepared from naphthenic or aromatic crudes and having a Saybolt viscosity at 210 F. of 45 to 90 seconds and a viscosity index of 0 to 50. However, in certain types of Diesel engine and other gasoline engine service, oils of higher viscosity index are often preferred, for example, up to 75 to 100, or even higher, viscosity index.

In addition to the material to be added according to the present invention, other agents may also be used such as dyes, pour depressors, heat thickened fatty oils, sulfurized fatty oils, organo-metallic compounds, metallic or other soaps, sludge dispersers, other anti-oxidants, thickeners, viscosity index improvers, oiliness agents, resins, rubber, olefin polymers, voltolized fats, voltolized mineral oils, and/ or voltolized waxes and colloidal solids such as graphite or zinc oxide, etc. Solvents and assisting agents, such as esters, ketones, alcohols, aldehydes, halogenated or nitrated compounds, and the like may also be employed.

In addition to being employed in lubricants, the additive of this invention may be also used in motor fuels, hydraulic fluids, torque converter fluids, cutting oils, fluslr ing oils, turbine oils or transformer oils, industrial oils, process oils, gear lubricants, greases, and generally as anti-oxidants in oleaginous products.

What is claimed is:

1. An oil-soluble product prepared by reacting a polysulfide of an alkaline earth metal with a compound having the formula where R is selected from the group consisting of hydrogen atoms and alkyl radicals containing 1 to 16 carbon atoms, the reaction being carried out at about F. to about 570 F. for an extended period of time until said product contains a ratio of sulfur atoms to nitrogen atoms in the range of about 0.4 to 1.5, the proportion of metal polysulfide employed in the reaction being such as to provide sufiicient reactive sulfur atoms to produce said ratio of sulfur atoms to nitrogen atoms in said product.

2. Product according to claim 1 wherein the reaction is carried out at a temperature in the range of about 200 to 300 F.

3. Product according to claim 1 wherein said polysulfide has the formula where M is an alkaline earth metal and b is an integer of 2 to 5.

4. Product according to claim 1 wherein said compound is diphenylamine.

5. Product according to claim 1 wherein said compound is p,p' dioctyl diphenylamine.

6. Product according to claim 1 wherein the reaction is carried out for a period of time in the range of about 0.5 to 4 hours.

7. An oil-soluble product obtained by reacting CaS where b is an integer of 2 to S with diphenylamine, the reaction being carried out at a temperature in the range of about 200 to 300 F. for a period of time in the range of about 1 to 2 hours, the proportion of Cas employed in said reaction being sufficient to produce a ratio of sulfur atoms to nitrogen atoms in the range of 0.5 to 1.0 in said product.

8. An oil-soluble product obtained by reacting CaS where b is an integer of 2 to with p,p' dioctyl diphenylamine, the reaction being carried out at a temperature in the range of about 200 to 300 F. for a period of time in the range of about 1 to 2 hours, the proportion of CaS employed in said reaction being sufficient to produce a ratio of sulfur atoms to nitrogen atoms in the range of about 0.5 to 1.0 in said product.

9. A process for preparing an oil-soluble sulfurand nitrogen-containing product useful as an oxidation inhibitor which comprises forming a mixture of an alkaline earth metal polysulfide and a compound selected from the group consisting of diphenylamine and dialkyl derivatives of diphenylamine containing 1 to 16 carbon atoms in each alkyl group, the proportion of said metal polysulfide in said mixture being such as to providesuflicient reactive sulfur atoms so that said product contains a ratio of sulfur atoms to nitrogen atoms'in the range .of about 0.4 to 1.5, heating said mixture at an elevated temperature of about F. to about 570 F. to etfect a chemical reaction until said product contains sulfur and nitrogen atoms in said ratio, and recovering said product from the reaction mixture.

10. Process according to claim 18 wherein said mixture is heated at a temperature in the range of about 200 to 300 F. for a period of time in the range of about 0.5 to 4 hours.

References Cited in the file of this patent UNITED STATES PATENTS 282,835 Bernthsen Aug. 7, 1883 1,766,403 Schulemann June 24, 1930 2,162,686 De Eds June 13, 1939 2,165,493 Lubs et al. July 11, 1939 2,308,691 Hughes Jan. 19, 1943 2,316,903 Van Ess Apr. 20, 1943 

1. AN OIL-SOLUBLE PRODUCT PREPARED BY REACTING A POLYSULFIDE OF AN ALKALINE EARTH METAL WITH A COMPOUND HAVING THE FORMULA
 9. A PROCESS FOR PREPARING AN OIL-SOLUBLE SULFUR- AND NITROGEN-CONTAINING PRODUCT USEFUL AS AN OXIDATION INHIBITOR WHICH COMPRISES FORMING A MIXTURE OF AN ALKALINE EARTH METAL POLYSULFIDE AND A COMPOUND SELECTED FROM THE GROUP CONSISTING OF DIPHENYLAMINE AND DIALKYL DERIVATIVES OF DIPHENYLAMINE CONTAINING 1 TO 16 CARBON ATOMS IN EACH ALKYL GROUP, THE PROPORTION OF SAID METAL POLYSULFIDE IN SAID MIXTURE BEING SUCH AS TO PROVIDE SUFFICIENT REACTIVE SULFUR ATOMS SO THAT SAID PRODUCT CONTAINS A RATIO OF SULFUR ATOMS TO NITROGEN ATOMS IN THE RANGE OF ABOUT 0.4 TO 1.5, HEATING SAID MIXTURE AT AN ELEVATED TEMPERATURE OF ABOUT 175*F. TO ABOUT 570*F. TO EFFECT A CHEMICAL REACTION UNTIL SAID PRODUCT CONTAINS SULFUR AND NITROGEN ATOMS IN SAID RATIO, AND RECOVERING SAID PRODUCT FROM THE REACTION MIXTURE. 